Basic physical science informs us that the upper surfaces of liquids such as but not limited to water situated in a gravitational field will naturally define a level horizontal surface which is normal to the direction of the gravitational field, with a mild curvature equal to that of the approximate 4000 mile radius of the earth. Similarly, it has long been known based on this same science that the surfaces of liquids in two or more fluidically-interconnected liquid containers or columns in a gravitational field will define a level surface normal to the gravitational field, once the fluid communication between the columns reaches static equilibrium and all flow ceases. This scientific understanding has been applied to develop a wide array of leveling devices and methods for establishing level surfaces relative to the earth's gravitational field. It is through the use of measuring devices which establish such a level, that it is possible to construct buildings and homes which are upright with respect to the earth's gravitational field, and to ensure that other structures or sensitive instruments which require leveling such as but not limited to turbines are in fact are situated in a leveled manner.
The use of fluidically-interconnected containers or columns to establish a level has become such common practice, that it has obtained its own sub-classifications within class 33 for “geometrical instruments” of the United States Patent Classification (USPC) System. Specifically, subclass 33/300 for “indicator of direction of force traversing natural media” generally covers any “device or method for indicating a direction related to that of some force (e.g., magnetic field, gravity etc.), of the type which will pass through a natural media (e.g., air, earth, water).” Within this subclass, the finer subclass 33/365 for “level or plumb, terrestrial gravitation responsive” covers devices “responsive to terrestrial gravitation and establishing either a horizontal or a vertical direction.” And even further on point, subclass 33/367 for a “plural, similar, separable liquid columns system” covers a range of devices “including separable, independently movable liquid containers interconnected by a liquid conductor, the upper surfaces of the liquid in the containers establishing a horizontal direction.”
While the principle and practice of using the upper surfaces of liquids in separate but interconnected liquid containers to establish a horizontal (level) direction responsive to terrestrial gravitation is thus well established in the art, the problem of how to practice this art to achieve exceptionally-high, fine grade leveling precision at better than 10−4 inches over a distance exceeding a few feet is not well-established and remains a work in progress. For such high-precision leveling, “noise” factors come into play which can be ignored for less-fine leveling, but which cannot be ignored and must be systematically addressed, isolated, and eliminated to obtain high precision.
For example, a single bubble in the lines interconnecting the separate containers can modify the reading at the 10−4 inches level of precision. So too can a single dust particle on the surface of whatever device probes the water, or a gradient in temperature along the fluidic connection, or a difference in temperature between the fluid system and the ambient air. Too much bending or drooping in the tube interconnections can also modify a measurement. Even the surface tension of the fluid including the cohesion between fluid molecules and the adhesion between the fluid molecules and the container and the probing device can modify a measurement if not properly accounted for and addressed.
Some of the cautions mentioned above are most applicable to a measuring system utilizing one micrometer and a plurality of water cups as is disclosed in some of the invention embodiments here, and they arise because of the time it takes to perform a reading on multiple cups with one micrometer. In fact, at the 10−4 inches or better level of precision, if the radius of the surface for which one seeks to establish a level is greater than about 20 feet, the earth's curvature itself can skew the measurement if not properly accounted for, because the “level” surface being measured now covers a large enough portion of the earth's surface so that it is not flat, but possesses the very mild curvature of a spherical surface with a 3959 mile radius, namely, the tide-averaged mean radius of the earth. Thus, at this fine a scale of precision, one is measuring not only level, but also, flatness. Historically, this very phenomenon, in the form of ships disappearing in the distant horizon, contained the first Copernican clues of a round earth.
While a number of the patents which can be found in subclass 33/367 of the USPC such as U.S. Pat. No. 5,131,156; U.S. Pat. No. 3,269,023; U.S. Pat. No. 4,384,410; U.S. Pat. No. 4,686,773 all involve efforts to achieve some degree of precision for a gravitational leveling system using fluids in interconnected containers, they do not appear capable of 10−4 inches or better precision, and as is seen in FIG. 5 of U.S. Pat. No. 4,384,410, at least some of these devices rely upon supplementing the fluidic leveling device with computerized control circuitry that contributes to the establishment of the more-precise level. It is preferable to be able to establish a high-precision level simply, using only the science and technology of fluids and their response to gravity coupled with simple linear length measurement instruments such as micrometers, while omitting the use of or need for complex data processing or other cumbersome or expensive technologies.